Unfortunately I should admit that most people get into timeshare trap while they do not really need a timeshare.
As you became an owner of the property - you have responsibility for taxes, insurance, maintenance, etc - all these expenses are based on the fact of your ownership.
In additional - as you likely did not pay cash for the timeshare - you took a loan - thus you entered into relation with financial company or a bank that legally unrelated to the development company that sold you the timeshare. So you took responsibility to pay the loan back.
It is likely that you purchased the timeshare from development company which built the property, but in additional you are in contract with another company which manages the property.
It is not clear to whom you "agreed to deed back the property" - it is likely not the company from which the property was purchased - so it is not really "back". The fair market value of the timeshare is likely less than the amount you owe.
The bank might agree to forgive you the loan as part of the transaction - so you will not owe anything after that. Is -so - the bank will issue the form 1099C - http://www.irs.gov/pub/irs-pdf/f1099c.pdf that would make forgiven amount deemed your taxable income.
You should look at the box 2 - that amount is considered your income and in general is taxable. However there are some exemptions. If you was insolvent at the time of cancellation - you need to file a form 982 - to proof your insolvency - and may not include all or part of canceled dent into taxable income.
Please see the IRS Publication 908 Bankruptcy Tax Guide - http://www.irs.gov/pub/irs-pdf/p908.pdf - with example of the form 982 on the last page.